CXD1177Q 데이터 시트보기 (PDF) - Sony Semiconductor

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CXD1177Q

8-bit 40MSPS YC 2-channel D/A Converter

Sony Semiconductor 

CXD1177Q

Notes on Operation

• How to select the output resistance

The CXD1177Q is a D/A converter of the current output type. To obtain the output voltage connect the

resistance to the current output pins Y0, C0. For specifications we have;

Output full scale voltage VFS = 1.8 to 2.2 [V]

Output full scale current IFS = less than 15 [mA]

Calculate the output resistance value from the relation of VFS = IFS × ROUT. Also, 16 times resistance of the

output resistance is connected to reference current pin IREF. In some cases, however, this turns out to be a

value that does not actually exist. In such a case a value close to it can be used as a substitute. Here

please note that VFS becomes VFS = VREF × 16ROUT/RIR. ROUT is the resistance connected to the current

output pins YO and CO while RIR is connected to IREF. Increasing the resistance value can curb power

consumption. On the other hand glitch energy and data settling time will inversely increase. Set the most

suitable value according to the desired application.

• Phase relation between data and clock

To obtain the expected performance as a D/A converter, it is necessary to set properly the phase relation

between data and clock applied from the exterior. Be sure to satisfy the provisions of the setup time (tS) and

hold time (tH) as stipulated in the Electrical Characteristics.

• Power supply and grand

To reduce noise effects separate analog and digital systems in the device periphery. For the power supply

pins, both digital and analog, bypass respective grounds by using a ceramic capacitor of about 0.1 µF, as

close as possible to the pin.

• Latch up

AVDD and DVDD have to be common at the PCB power supply source. This is to prevent latch up due to

voltage difference between AVDD and DVDD pins when power supply is turned ON.

• YO and IO pins

The YO and IO pins are the inverted current output pins described in the Pin Description. The sums shown

below become the constant value for any input data.

a) The sum of the currents output form YO and YO

b) The sum of the currents output form CO and CO

However, the performances such as the linearity error of the inverted current output pin output current is not

guaranteed.

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